Chelmsford, Mass. — Valerie Celeste Coffey is a woman on a mission. For six years, her small group of local atheists has gathered to exchange bemused stories about the things Christians do in worship and swap tips for raising confident skeptics.

But on a recent Wednesday evening here at the Java Room cafe, Ms. Coffey said the time had come to take the meetings in hand.

"I don't think this group has a vision," said Coffey, a freelance editor who lives in nearby Boxborough, Mass. "We need to figure out what our values are."

The ranks of nonbelievers are on the rise, research suggests, and as they seek out each other online and in small groups, they are increasingly looking to do more than just vent.

Some are adopting rituals themselves, from de-baptisms to wedding ceremonies, as a way to cement ties among members. Others are organizing science-related outings or enrolling in community-service programs. Nationwide, atheists' groups are now treading, sometimes gingerly, into unfamiliar territory.

"This is the transition moment right now," says Dale McGowan, author of "Parenting Beyond Belief: On Raising Ethical, Caring Kids Without Religion." "Some groups are really diving in [to foster a robust sense of community], and some of them are holding their noses and standing on the diving board. They're not quite sure what to do."

Some 15 percent of Americans claim no religious affiliation, up from 8.2 percent in 1990, according to Trinity College's American Religious Identification Survey, released in March. Also, the American Humanist Association claims 20,000 financial supporters. That marks a doubling from five years ago, says spokeswoman Karen Frantz.

Moreover, signs point to non-believers seeking fellowship as never before. During the first five months of 2009, 95 new atheist groups have formed through meetup.com, bringing the US total to 372. That's up from 59 in 2005, says Blair Scott, director of national affiliates for American Atheists, a networking and advocacy organization. Known parenting groups for nonbelievers have proliferated from just one in 2005 to 33 in 2009, adds Mr. McGowan, the author.

The intersection of the two trends is evident across the United States. For example, the North Alabama Freethought Association, which has grown from 50 members in 2006 to 350 today, drew 30 people to a camping event in May and runs regular outings to visit caves or other science-related sites.

"It used to be that these atheist groups ... met almost in hiding," says American Atheists spokesman David Silverman. "Now they're doing a lot more stands at town parties, a lot more trash pickups, a lot more blood donations – a lot more stuff that gets their group out and noticed."

Some say such initiatives are necessary to improve an image problem. Rebecca Grieve founded South Lake Atheists and Freethinkers in Groveland, Fla., last year because she felt the nearby atheist group in Orlando "wasn't doing enough in the community." Through an Adopt-A-Lake project, the new group monitors a section of Lake Minneola and promotes its efforts on a big sign at Clermont Waterfront Park.

"A lot of atheist groups are really negative," says Ms. Grieve, who now lives in Derry, N.H., and describes herself as a secular humanist. "They're not standing for anything. They're not making a difference.... I want to be accepted just like everybody else. We need to be showing people through example that we're decent people."

For some, however, the status quo suits just fine. Of the monthly Atheists of Greater Lowell (Mass.) gatherings, where no one convenes or adjourns the group, Paul Ratner of Lowell says: "I like this group as it is now."

Rob Butler of Westford. Mass., agrees: "I love coming here because I can just say whatever's on my mind, and people won't be offended by it."

In some ways, the lack of structure or ritual has been a defining characteristic of atheist groups. McGowan notes that many atheists bristle at ritual because it feels too religious or superstitious. American Atheists' Mr. Silverman insists, "there are no rituals with us."

But America's 27 Ethical Societies, which attract many nontheist attendees to their humanist "platforms," or services, see growing interest in rituals, ranging from children's education to weddings, according to membership chairman Thomas Hoeppner.

Through ritual, "you build up not just common intellectual values, but the emotional and personal connection with people," says Mr. Hoeppner, a member of the Ethical Humanist Society of Chicago. "That's what it's all about."

"So when one of my dear friends in his 80s lost his wife, he'd be over at our house every Sunday afternoon for dinner," he says. "That's a ritual for us."

In Florida, atheists are pioneering a new ritual: de-baptism. Since last year, American Atheists' Florida state director Greg McDowell has been donning a mock clerical robe and officiating at services where family and friends come to watch the baptized renounce their baptisms.

The events spoof baptisms by using blow-dryers in the place of baptismal waters. They culminate in certificates for the "de-baptized" and letters to churches requesting that the names of those de-baptized be removed from baptismal rolls.

Elsewhere, ties that bind the faithless continue to grow stronger, even without ritual per se. After one member of the North Alabama Freethought Association was robbed earlier this year, fellow members collected a few hundred dollars to see him through to payday. And when another was injured in a motorcycle accident, atheists brought meals every day for him and his caretakers.

"It makes me sit back and smile to know that this community has built itself up in a way that they're looking out for each other, watching each other's backs, and supporting each other," says Mr. Scott, who founded the Alabama group six years ago. "It almost makes me feel fatherly – like you raised your child right."